Wavelength-converting member

ABSTRACT

A wavelength-converting member with high emission intensity and that is superior in weather resistance and reliability is obtained. There is provided a phosphor on which a cleaning treatment and/or a coating treatment are/is performed is contained in a glass material having a composition of SiO 2 : 30 to 50%, Li 2 O: 0 to 15%, Na 2 O: 0 to 10%, K 2 O: 0 to 10%, Li 2 O+Na 2 O+K 2 O: 20 to 30%, B 2 O 3 :5 to 15%. MgO: 0 to 10%, BaO: 0 to 10%, CaO: 0 to 10%, SrO: 0 to 10%, Al 2 O 3 : 0 to 10%, ZnO: 0 to 15%, TiO 2 : 10 to 20%, Nb 2 O 5 : 1 to 5%, La 2 O 3 : 0 to 5%, and TiO 2 +Nb 2 O 5 +La 2 O 3 : 11 to 20% by mole percentage.

JOINT RESEARCH AGREEMENT

The invention described herein is based on a Joint Research Agreementbetween Nichia Corporation and Nippon Electric Glass Co., Ltd.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a wavelength-converting member using aphosphor.

2. Description of the Related Art

In a wavelength-converting member using a phosphor, light is emitted bymixing phosphor powder, for example, with a molding resin consisting ofan organic or an inorganic binder resin that shields a light emittingface of a light emitting element, molding the mixture, absorbing a lightemission of the light emitting element, and transforming it to a fixedwavelength. However, in a light emitting device using a light emittingdiode etc., when a wavelength-converting member is constituted with aphosphor layer containing an organic binder resin, the organic binderresin itself deteriorates by light of high output in the shortwavelength region (the ultraviolet region to the blue region) and thereis a problem that emission brightness decreases largely by coloring,etc.

In Japanese Patent Application Laid-Open (JP-A) No. 2004-161871, it isproposed that a mixture of phosphor powder, an organic binder resin, aninorganic sintering assistant and the like is molded into a desiredshape, and the organic binder resin that becomes a cause of thedeterioration of the phosphor layer is sintered and removed.

In JP-A No. 2003-258308, a wavelength-converting member is proposed inwhich an inorganic phosphor is dispersed in a glass.

However, there is a case that sufficient weather resistance andreliability cannot be obtained in the method of sintering and removingthe organic binder resin. Further, in the case of sintering at hightemperature, the phosphor deteriorates or decomposes depending on thetype of the phosphor, and there is a case that the emission intensitydecreases.

Further, also in the case of dispersing the phosphor into a glass, thephosphor deteriorates or decomposes because the process temperaturebecomes high, and there is a case that the emission intensity decreases.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide awavelength-converting member that has high emission intensity and thatis superior in weather resistance and reliability.

In the wavelength-converting member in the present invention, a phosphoron which a cleaning treatment and/or a coating treatment are/isperformed is contained in the glass material having a composition ofSiO₂: 30 to 50%, Li₂O: 0 to 15%, Na₂O: 0 to 10%, K₂O: 0 to 10%,Li₂O+Na₂O+K₂O: 20 to 30%, B₂O₃: 5 to 15%, MgO: 0 to 10%, BaO: 0 to 10%,CaO: 0 to 10%, SrO: 0 to 10%, Al₂O₃: 0 to 10%, ZnO: 0 to 15%, TiO₂: 10to 20%, Nb₂O₅: 1 to 5%, La₂O₃: 0 to 5%, and TiO₂+Nb₂O₅+La₂O₃: 11 to 20%by mole percentage.

In the present invention, a phosphor on which a cleaning treatmentand/or a coating treatment are/is performed is used as the phosphor. Byusing a phosphor on which a cleaning treatment and/or a coatingtreatment are/is performed according to the present invention, theemission intensity can be increased.

An example of the cleaning treatment in the present invention is aprocess of cleaning the surface of phosphor powder with an acid or purewater. An inorganic acid such as nitric acid and hydrochloric acid andan organic acid such as acetic acid can be used as the acid. Aconcentration of a solution is preferably in the range of 0.1% to 50% inthe case of performing cleaning with an acid solution. An example of amethod of performing cleaning includes a method of pouring a solutionsuch as an acid, a phosphor, and pure water into a container such asbeaker, cleaning by stirring with a stirring rod etc. By performing acleaning treatment, impurities such as non-reacted raw material and fluxexisting near the surface of the phosphor powder can be removed, andemission efficiency of the phosphor can be increased.

Further, an example of the coating treatment in the present invention isa process of coating the surface of the phosphor particle with fineparticles. Examples of the fine particles include a rare earth elementsuch as Sc, Y, La, Gd, Tb, and Lu, an alkali earth metal element such asCa and Sr, an oxide of an element such as Nb, Ta, Mo, W, Zn, Sn, Sb, Al,Si, and Ti, orthophosphate, and pyrophosphate. The coating amount ispreferably 0.01% by mass to 50% by mass.

An example of a specific method of the coating treatment is a method ofperforming an annealing treatment in a reduction atmosphere or a neutralatmosphere after mixing and stirring the phosphor particles and the fineparticles with a high speed and attaching the fine particles to thesurface of the phosphor particle. Examples of the reduction atmosphereinclude H₂ and NH₃, and examples of the neutral atmosphere include N₂and Ar. An example of a temperature and time of the annealing treatmentis generally 100° C. to 1700° C. and 0.1 hour to 10 hours.

Further, other methods of the coating treatment in the present inventioninclude a surface coating treatment by sol/gel. By performing a coatingtreatment on the surface of the phosphor particles according to thepresent invention, the emission intensity of the phosphor can beimproved.

In the present invention, the phosphor on which the cleaning treatmentand/or the coating treatment are/is performed as described above isincluded in the glass material of the specific composition describedabove. Therefore, the wavelength-converting member in the presentinvention can be manufactured by performing the cleaning treatmentand/or the coating treatment on the phosphor and then dispersing thephosphor powder into the glass material by mixing with the glassmaterial of the specific composition described above and melting theglass material.

By including the phosphor into the glass material of the specificcomposition described above according to the present invention, awavelength-converting member that is superior in weather resistance andreliability can be made. The glass material of the above-describedcomposition has a low softening point in general, for example, it is600° C. or less, and preferably in the range of 500° C. to 560° C. Byusing such glass material, the reaction between the glass and thephosphor when the phosphor is included in the glass material can bereduced, and a wavelength-converting member with high emission intensitycan be made by suppressing deterioration or decomposition of thephosphor. Further, by using the glass material as a dispersion medium ofthe phosphor, a wavelength-converting member that is superior in weatherresistance and reliability can be made.

The reason for prescribing each content of the glass component in theabove-described glass material is as follows.

SiO₂ is a component constituting a skeleton of the glass. When itscontent becomes less than 30%, chemical durability tends to deteriorate.On the other hand, when it becomes more than 50%, the sintering(calcining) temperature becomes high and the phosphor easilydeteriorates. The more preferred range of SiO₂ is 35% to 45%.

B₂O₃ is a component to remarkably improve the melting property bylowering the melting temperature of the glass. When its content becomesless than 5%, this effect becomes difficult to obtain. On the otherhand, when it becomes more than 15%, chemical durability tends todeteriorate. The more preferred range of B₂O₃ is 7% to 14%.

MgO is a component to improve the melting property by lowering themelting temperature of the glass. When its content becomes more than10%, chemical durability tends to deteriorate. The more preferred rangeof MgO is 0% to 7%.

CaO is a component to improve the melting property by lowering themelting temperature of the glass. When its content becomes more than10%, chemical durability tends to deteriorate. The more preferred rangeof CaO is 0% to 7%.

SrO is a component to improve the melting property by lowering themelting temperature of the glass. When its content becomes more than10%, chemical durability tends to deteriorate. The more preferred rangeof SrO is 0% to 7%.

BaO is a component to improve the melting property by lowering themelting temperature of the glass and to suppress a reaction with thephosphor. When its content becomes more than 10%, chemical durabilitytends to deteriorate. The more preferred range of BaO is 2% to 8%.

Al₂O₃ is a component to improve chemical durability. When its contentbecomes more than 10%, the softening point of the glass tends toincrease. The more preferred range of Al₂O₃ is 0% to 7%.

ZnO is a component to improve the melting property by lowering themelting temperature of the glass. When its content is more than 15%, thesoftening point of the glass tends to increase. The more preferred rangeof ZnO is 5% to 13%.

Li₂O has a large effect to lower the softening point the most among thealkali metal components. Its content is 0 to 15%, preferably 3% to 13%,and further preferably 4% to 12%. When Li₂O exceeds 15%, devitrificationoccurs easily. Furthermore, the amount of alkali elution increases andweather resistance decreases.

Na₂O is a component to lower the softening point. Its content is 0% to10%, and preferably 3% to 8%. When Na₂O exceeds 10%, the amount ofalkali elution increases and weather resistance decreases.

K₂O has an effect to lower the softening point. However, the amount ofalkali elution increases and the weather resistance decreases. Becauseof this, the content of K₂O is limited to 0% to 10%, and preferably to3% to 8%.

Moreover, the total amount of Li₂O, Na₂O, and K₂O, which are alkalimetal oxides, is desirably made to 20% to 30% in order to suppress theincrease of the softening point and the decrease of weather resistance.

TiO₂ is a component to improve weather resistance. Its content is 10% to20%, and preferably 11% to 17%. When TiO₂ exceeds 20%, a crystal havingTiO₂ as a core becomes easy to deposit and devitrification increases. Onthe other hand, when it is less than 10%, weather resistance decreases.

Nb₂O₅ is a component to improve weather resistance while suppressing thedeposition of the crystal originated in TiO₂. Its content is 1% to 5%,and preferably 2% to 4%. When Nb₂O₅ exceeds 5%, the crystal formed withTiO₂—Nb₂O₅ becomes easy to deposit, and devitrification increases. Onthe other hand, when it is less than 1%, the effect to suppress thedeposition of the crystal originated in TiO2 becomes small and weatherresistance remarkably decreases.

La₂O₃ is a component to improve weather resistance. Its content is 0% to5%, and preferably 1% to 4%. When La₂O₃ exceeds 5%, a crystal havingLa₂O₃ as a core becomes easy to deposit and devitrification increases.

Moreover, in order to suppress the decrease of weather resistance, thetotal amount of TiO₂, Nb₂O₅, and La₂O₃ is desirably set to 11% to 20%.

Further, besides the above-described components, various components canbe added in the range where the main point of the present invention isnot spoiled. For example, Sb₂O₃, P₂O₅, Ta₂O₅, Gd₂O₃, WO₃, Bi₂O₃, ZrO₂,etc. may be added.

The phosphor that can be used in the present invention includes analuminate phosphor activated with cerium (Ce), represented by a generalformula M₃(Al_(1−v)Ga_(v))₅O₁₂: Ce (in the formula, M is at least onekind selected from Lu, Y, Gd, and Tb, and v satisfies 0≦v≦0.8). Bysetting v in the above-described range, a phosphor with high emissionbrightness can be made. The aluminate phosphor in the present inventioncan emit light of yellow to green by absorbing from near ultraviolet toblue light.

The phosphor that can be used in the present invention includes anitride phosphor activated with europium (Eu), represented by a generalformula M′_(w)Al_(x)Si_(y)B_(z)N_(((2/3)w+x+(4/3)y+z)): Eu (in theformula, M′ is at least one kind selected from Mg, Ca, Sr, and Ba, andw, x, y, and z satisfy 0.5≦w≦3, x=1, 0.5≦y≦3, and 0≦z≦0.5,respectively). By setting w, x, y, and z in the above-described range, aphosphor with high emission brightness can be made. This nitridephosphor is a phosphor that emits red light by absorbing from nearultraviolet to blue light. The light from near ultraviolet to blue islight of which the peak wavelength is generally in the range of 360 nmto 500 nm. Further, red light is light of which the peak wavelength isgenerally in the range of 600 nm to 700 nm. Further, the light of greento yellow emitted by the above-described aluminate phosphor is light ofwhich the peak wavelength is generally in the range of 510 nm to 580 nm.

By using the above-described aluminate phosphor and the nitride phosphorin combination as the phosphor, a wavelength-converting member thatemits white light can be made.

The content of the phosphor in the wavelength-converting member in thepresent invention is selected appropriately depending on the type of thephosphor, and is not especially limited. However, in general, it ispreferably in the range of 1 to 25% by weight, and more preferably inthe range of 8 to 15% by weight. When the content of the phosphor is toomuch, bubbles generated when the phosphor and a glass material are mixedand sintered tend to remain easily in a sintered body, and as a result,transmissivity decreases and emission intensity easily decreases.Further, when the content of the phosphor is too little, the ratio ofexcited light becomes too much and chromaticity tends to shift.

The wavelength-converting member in the present invention can beproduced by mixing a phosphor and a glass material and sintering thismixed powder at a temperature of the softening point of the glassmaterial or more. A wavelength-converting member of a fixed shape can bemanufactured by manufacturing a preformed body of a fixed shape byadding a resin binder depending on necessity and pressure-molding, andby calcining it.

According to the present invention, a wavelength-converting member canbe made that has high emission strength and that is superior in weatherresistance and reliability.

Therefore, the wavelength-converting member in the present invention canbe used as a wavelength-converting member in an emission device in whichweather resistivity and reliability are desired such as a signal light,a lighting, a display, and an indicator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a FIGURE showing an emission spectrum of thewavelength-converting member in Example 2 and Reference Example 2according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EXAMPLES

The present invention is explained by specific examples below. However,the present invention is not limited to the following examples.

Examples 1 to 9 and Reference Examples 1 to 3

A wavelength-converting member was manufactured using the phosphor andthe glass material shown in Table 1 at the compounding ratio shown inTable 1. Specifically, a wavelength-converting member was obtained bysufficiently mixing the phosphor and the glass material shown in Table 1with a mixing machine and a dry method, filling a crucible with this rawmaterial, calcining it at 540° C. for 20 minutes in an air atmosphere,and molding it into a fixed shape. Moreover, it was heated and calcinedat 540° C. for 20 minutes in Reference Example 3.

A LAG phosphor (an aluminate phosphor) of the composition shown belowand a CASBN phosphor (a nitride phosphor) of the composition shown belowwere used as the phosphor.

LAG phosphor: (Lu_(0.94))₃Al₅O₁₂: Ce_(0.06)

CASBN phosphor: Ca_(0.99)Al_(1.00)Si_(1.00)B_(0.10)N_(3.1): Eu_(0.01)

Further, “glass in the present invention” having a composition in therange of the present invention shown below and “comparison glass” havinga composition out of the range of the present invention were used as theglass material. Moreover, “%” in the glass composition is “mol %”.

Glass in the present invention:

40% SiO₂-10% B₂O₃-10% TiO₂-10% Li₂O-7% K₂O-6% Na₂O-3% Nb₂O₅-10% ZnO-4%BaO

Comparison glass: 11% SiO₂-43% B₂O₃-11% Na₂O-35% ZnO

<Treatment of LAG Phosphor>

A cleaning treatment was performed on a LAG phosphor using a nitric acidsolution (concentration about 2%) for what is described as “nitric acidcleaning.” Specifically, 350 g of dilute nitric acid (60%) was addedinto 10 liters of pure water and mixed in a fixed container. The LAGphosphor was put in it and stirred. An Al₂O₃ coating treatment wasperformed after performing the above-described nitric acid cleaning onthe LAG phosphor for what is described as “nitric acid cleaning • Al₂O₃coating.” Specifically, in Al₂O₃ coating treatment, the coatingtreatment was performed by adding 100 g of Al₂O₃ fine particles to 1000g of LAG phosphor on which the nitric cleaning is performed, mixing andstirring these with high speed, and then performing an annealingtreatment at 1000° C. for 5 hours in a nitrogen atmosphere.

<Treatment of CASBN Phosphor>

An Al₂O₃ coating treatment was performed on a CASBN phosphor in the samemanner as the above-described Al₂O₃ coating of the LAG phosphor byadding 30 g of Al₂O₃ fine particles to 300 g of CASBN phosphor, mixingand stirring with high speed, and then performing an annealing treatmentin a nitrogen atmosphere for what is described as “Al₂O₃ coating.”

A SiO₂ coating treatment was performed by adding 30 g of SiO₂ fineparticles to 300 g of CASBN phosphor, mixing and stirring with highspeed, and then performing an annealing treatment at 1000° C. for 5hours in a nitrogen atmosphere for what is described as “SiO₂ coating.”

TABLE 1 Type Phosphor LAG Phosphor CASBN Phosphor Glass Material Glassin Present Invention Example 1 Treatment Nitric Acid Cleaning None —Amount Used 10 g 2 g 88 g Example 2 Treatment Nitric Acid Cleaning Al₂O₃Coating — Amount Used 10 g 2 g 88 g Example 3 Treatment Nitric AcidCleaning Al₂O₃ Coating — Amount Used  7 g 3 g 90 g Example 4 TreatmentNitric Acid Cleaning SiO₂ Coating — Amount Used  7 g 3 g 90 g Example 5Treatment Nitric Acid Cleaning•Al₂O₃ Coating Al₂O₃ Coating — Amount Used10 g 2 g 88 g Example 6 Treatment Nitric Acid Cleaning•Al₂O₃ CoatingAl₂O₃ Coating — Amount Used  7 g 3 g 90 g Example 7 Treatment NitricAcid Cleaning Al₂O₃ Coating — Amount Used 10 g 2 g 88 g Example 8Treatment Nitric Acid Cleaning Al₂O₃ Coating — Amount Used 10 g 2 g 88 gExample 9 Treatment Nitric Acid Cleaning Al₂O₃ Coating — Amount Used 10g 2 g 88 g Reference Treatment — None — Example 1 Amount Used — 2 g 98 gReference Treatment None None — Example 2 Amount Used 10 g 2 g 88 gGlass Material Comparison Glass Reference Treatment Nitric Acid CleaningAl₂O₃ Coating — Example 3 Amount Used 10 g 2 g 88 g[Evaluation of Emission Color and Emission Intensity]

The emission color and the emission intensity were evaluated on each ofthe obtained wavelength-converting members.

The emission color was evaluated by using a chromaticity meter togetherwith observing visually the color of light coming out through thewavelength-converting member when excited light of wavelength 400 nm wasapplied to the wavelength-converting member. The measurement results ofthe emission color distinguished visually and the color coordinatemeasured with a chromaticity meter are shown in Table 2.

The emission brightness was evaluated by measuring the emissionbrightness of the light coming out through the wavelength-convertingmember when excited light of wavelength 460 nm is applied to thewavelength-converting member and making this emission brightness asemission brightness to the emission brightness (100%) in the case ofusing a wavelength-converting member consisting of a YAG phosphor of aresin seal existing conventionally. It is shown in Table 2 as “relativebrightness to YAG (%).”

TABLE 2 Color Coordinate Relative Brightness Emission Color x y to YAG(%) Example 1 White 0.333 0.325 85 Example 2 White 0.351 0.348 96Example 3 White 0.330 0.325 90 Example 4 White 0.348 0.335 91 Example 5White 0.320 0.323 88 Example 6 White 0.350 0.353 98 Example 7 White0.349 0.347 95 Example 8 White 0.352 0.349 96 Example 9 White 0.3480.348 96 Reference White 0.653 0.332 20 Example 1 Reference White 0.3200.323 82 Example 2 Reference White 0.345 0.335 76 Example 3

As shown in Table 2, it is found that white with a good color phase canbe obtained with high emission brightness in the wavelength-convertingmember of Examples 1 to 9 in which a phosphor on which the cleaningtreatment and/or the coating treatment are/is performed according to thepresent invention is used and this phosphor is included in the glassmaterial with a composition in the range of the present invention.

On the other hand, in the wavelength-converting member in ReferenceExample 2 using a phosphor on which the cleaning treatment and thecoating treatment are not performed and Reference Example 3 using aglass material with a composition outside of the range of the presentinvention, the decrease of the emission brightness is a little. However,the ASBN phosphor is hardly emitting, and a wavelength-converting memberwith a good color rendering property cannot be obtained. Further, inReference Example 1 in which a LAG phosphor is not used, white lightwith a good color phase cannot be obtained, and the emission brightnessbecome considerably low.

[Measurement of Emission Spectrum]

The emission spectrum was measured on the wavelength-converting memberin Example 2 and Reference Example 2. The emission spectrum of lightcoming out through the wavelength-converting member when excited lightof wavelength 460 nm is applied to the wavelength-converting member wasmeasured. The measurement result is shown in FIG. 1.

As shown in FIG. 1, in the wavelength-converting member in Example 2,because the CASBN phosphor on which the coating treatment is performedis used, the CASBN phosphor emits light, and energy intensity around 650nm that is the emission region of the CASBN phosphor is high. On theother hand, in Reference Example 2, because the coating treatment is notperformed on the ASBN phosphor and the CASBN phosphor does not emitlight or emits a little light even if it emits light, the energyintensity around 650 nm is low. Moreover, because the amount of theCASBN phosphor added is relatively smaller than the LAG phosphor, a risedoes not exist in the emission region like the emission of the LAGphosphor (around 530 nm).

1. A wavelength-converting member, containing a phosphor on which acleaning treatment and/or a coating treatment are/is performed, in aglass material having a composition of SiO₂: 30 to 50%, Li₂O: 0 to 15%,Na₂O: 0 to 10%, K₂O: 0 to 10%, Li₂O+Na₂O+K₂O: 20 to 30%, B₂O₃: 5 to 15%,MgO: 0 to 10%, BaO: 0 to 10%, CaO: 0 to 10%, SrO: 0 to 10%, Al₂O₃: 0 to10%, ZnO: 0 to 15%, TiO₂: 10 to 20%, Nb₂O₅: 1 to 5%, La₂O₃: 0 to 5%, andTiO₂+Nb₂O₅+La₂O₃: 11 to 20% by mole percentage.
 2. Thewavelength-converting member according to claim 1, containing, as thephosphor, an aluminate phosphor activated with cerium (Ce), representedby a general formula M₃ (Al_(2-v)Ga_(v))₅O₁₂: Ce, wherein M is at leastone kind selected from Lu, Y, Gd, and Tb, and v satisfies 0≦v≦0.8. 3.The wavelength-converting member according to claim 1, containing, asthe phosphor, a nitride phosphor activated with europium (Eu),represented by a general formulaM′_(w)Al_(x)Si_(y)B_(z)N_(((2/3)w+x+(4/3)y+z)): Eu, wherein M′ is atleast one kind selected from Mg, Ca, Sr, and Ba, and w, x, y, and zsatisfy 0.5≦w≦3, x=1, 0.5≦y≦3, and 0≦z≦0.5, respectively.
 4. Thewavelength-converting member according to claim 2, containing, as anadditional phosphor, a nitride phosphor activated with europium (Eu),represented by a general formulaM′_(w)Al_(x)Si_(y)B_(z)N_(((2/3)w+x+(4/3)y+z)): Eu, wherein M′ is atleast one kind selected from Mg, Ca, Sr, and Ba, and w, x, y, and zsatisfy 0.5≦w≦3, x=1, 0.5≦y≦3, and 0≦z≦0.5, respectively.